Rehabilitating pkglint

### [@schmonz](https://twitter.com/schmonz)
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### [@schmonz](https://twitter.com/schmonz)
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# Rehabilitating pkglint

## Amitai Schlair, The NetBSD Project

### pkgsrcCon Berlin 2013/03/23

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### [PR pkg/46570 infelicities in pkglint](http://gnats.netbsd.org/46570)

"A good start would be rewriting it not in perl."
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.right-column[
### [Things You Should Never Do, Part I](http://www.joelonsoftware.com/articles/fog0000000069.html)

"When you throw away code and start from scratch, you are throwing
away all that knowledge. All those collected bug fixes. Years of
programming work."
]

.right-column[
"It's important to remember that when you start from scratch there
is absolutely no reason to believe that you are going to do a better
job than you did the first time."
]

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### Local `git`

$ echo .git >> ~/.cvsignore
    $ echo CVS >> ~/.gitignore_global
    $ cd $PKGSRCDIR/pkgtools/pkglint
    $ git init
    $ git add .
    $ git commit -am 'Add pkglint to git for offline hacking.'
    $ git checkout -b rehab
    
    $ cd $PKGSRCDIR/pkgtools/pkglint
    $ git checkout master
    $ cvs update
    $ git commit -am 'Track upstream changes from pkgsrc CVS.'
    $ git checkout rehab
    $ git rebase master
    $ vi files/pkglint.t files/pkglint.pl && make test && make clean
    $ git commit -am 'More cool stuff on my branch.'
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### I've been writing a lot of Perl lately

### I know a way to revive legacy code
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### Test-Driven Development

* Misnomer!
* Design technique (happens to result in automated tests)
* Programmer documentation (happens to be executable)

TDD leads to code that _looks like_ it was written by someone
careful, skillful, and tasteful.
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### "Test-Eventually Development"

* We didn't write pkglint test-first
* Design suffered
* Programmer documentation suffered

Whether or not we decide to rewrite pkglint, first we have to
understand and document its current behavior.

Never too late to test first. Just a bit more difficult.
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### In `pkgsrc-current`

* Convert to ["modulino"](http://www.drdobbs.com/scripts-as-modules/184416165)
* Add a [test script](http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/pkgtools/pkglint/files/pkglint.t)
* Hook it up to `make test` (just barely)
* Write a few tests (very simple)
* Prove that they fail when they should

Approved-by: `wiz`
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### In my `git`

* Add ["characterization tests"](https://en.wikipedia.org/wiki/Characterization_test) over a few mature packages
* Extract some Perl classes to separate files
* Fix `make test` (no custom settings needed)
* Deepen an existing test to prepare for [refactoring](https://en.wikipedia.org/wiki/Refactoring)
* Change huge `if/elsif/else` block to dispatch table
* Fix a bug (!) found during refactoring

Planning to merge to `pkgsrc`. In the meantime, see
[GitHub](https://github.com/schmonz/pkglint/tree/rehab).
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# A bit of the old code-reading

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### pkglint isn't such a big deal

### But `pkgsrc/mk` is
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* Cover infrastructure code with automated tests
* Gain shared understanding of complex internals
* Freely and safely change them for the better
* Keep what makes `pkgsrc` special
* Push `pkgsrc` forward
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### "Never too late to test first"

* Tangle of implementation languages
* Tangle of dependencies
* Progress won't be fast
* The alternative is worse
* We'll have to work together
* We'll have to be patient and persistent
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# FIN